Introduction to the HD25.2 portable turbidimeter
The HD25.2 is a digital turbidity meter for laboratory and mobile use, suitable for measurements in drinking water, waste water and process liquids. The working principle is based on the nephelometric (90° scattered light sensor) method. It is equipped with three light detectors and two LED light sources (white and infrared) which are permanently kept under control in order to guarantee long-term stability. The instrument performs measurements according to the standards EPA 180.1, ISO-NEPH (ISO 7027), EBC and ASBC. It is also able to carry out measures of transmission factor percentage of white and infrared light.
Nephelometers measure the intensity of light scattered by contaminants such as suspended and colloidal matter like clay and silt, and microscopic organisms. Turbidimeters using the nephelometric principal compare the light scattered due to contamination with the light scattering from a standard reference suspension. The result is a measurement of turbidity in NTUs - Nephelometric Turbidity Units.
The initial factory calibration is based on Formazin primary standard. For routine calibration a set of stabilized secondary standard solutions is available:
STCAL (Turbidity standards for calibration):
STCAL 1 less than 0,05 NTU
STCAL 2 equal to 8 NTU
STCAL 3 equal to 80 NTU
STCAL 4 equal to 800 NTU.
EPA180.1/ ISO-NEPH (ISO 7027) / EBC / ASBC / White %T and IR %T
EPA180.1: 0-1000 NTU
ISO-NEPH: 0-1000 FNU
EBC: 0-250 EBC
ASBC: 0-999 ASBC
WHITE %T: 0-100%T
IR %T: 0-100%T
+/- 2% of reading + 0.01 NTU (0-500 NTU) +/- 3% of reading (500 - 1000 NTU)
+/- 2% of reading or 0.01 NTU
0.01 NTU (0 - 9.99 NTU)
0.1 NTU (10-99.9 NTU)
1 NTU (100 - 1000 NTU)